Accelerometer



J. E. BEVINS Feb. 19, 1946;

ACCELEROMETER .Filed May 19, 1943 4Sheecs-Sheet 1 IN V EN TOR.

Feb. 19, 1946. J. E. BEVINS ACCELEROMETER Sheets-Sheet 2 Filed May 19, 1943 IN VEN TOR.

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INVENTOR.

Bevizwfi v BY Wm M Pmmd Feb. 1-9, 1946 I ACQELEROMETER James E. BevinsfHa'ckensack, NHL, assignor to Bendix Aviation Corporation, Bendix N. J., a:

corporation of Delaware --'Application May 19-, 1943, Serial No. 487,673

v 7 Claims. This invention relates to accelerometers for aircraft and more particularly to an accelerometer embodying a plurality of mass motivated pointers for indicating positive and negative maximum indications together with instantaneous indications, responsive to gravitational influ- 'ences'derived from a pre-set movable mass having a relatively long range of movement, so the maximum pointers are not moved by normal vertical vibrations, but only by. positive or negative accelerations.

Prior to the present invention, weight or mass actuated accelerometers required complicated damping mechanism to' prevent normal vertical vibrational indications of the pointers, as this fault seriously impaired the accurate indication of material abnormalaccelerated vertical indications. Such damping arrangements are not only complicated but prolong production; as it is extremely difilcult to calibrate such arrangements,

which include structural elements such as fly links, gears and pinions subject to Wear and breakage from abnormal accelerations caused by diving and the like.

With the present device, it is a relatively simple matter to calibrate and set the weight or mass so as to eliminate the need of prior art damper mechanisms, because proper throw or length of mass movement maybe adjusted or calibrated after the mechanism hasb'een assembled by the simple process of temporarily hooking an auxiliary testing weight on the cable similar to theone to be permanently installed; the only step in assembly necessary after calibration being to insertthe assembly into the shell or casing of the accelerometer.

produce a relatively long throw before drive is imparted to themaximum pointer mechanism.

Yet. another object is to provide a novel drive means operated from said weight movements adapted to drive a plurality of individually mounted pointers in either a clockwise or counter-clockwise direction to make either negative or positive indications in combination with an instantaneous indicating pointer.

- The above and further objects and novel features of the invention will more fully appear from thefollowing detailed description when the same Accordingly, one of'the objects of'this invention is to provide an accelerometer so constructed as to no longer need complicated damper mechanisms to damp out interfering vibrational indi- I cations. I

Another object is the provision of a simplified device having no gears or pinions and the likesubject to wear or breakage under excessive strain from sudden unusually rapid accelerations.

A further object is to provide a device of this class wherein no fly link is necessary because a spread of only 340 is coveredby the maximum pointers instead of 360.

Another object provides for morev eflicient cali bration of the device to speed up plant production.

Yet another object is toprovide a novel means for mounting an accelerometer weight so as to is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for purposes of illustration only and are not intended as a definition I of the limits of the invention, reference for this latter purpose, being had to the appended claims.

In the drawings wherein like reference char- .acters refer to like parts throughout the several views Figure 1 is a' front elevation view of the assembled device.

Figure 2 is aside elevation view partly in section.

Figure 3 is a front elevation view 'of the frame without the casing.

Figure 4 is a side elevation view partly in cross section. Figure 5 is a rear elevation view of the frame.

Figure 6 is a plan view with a fragment of the main spring in cross section and with a lug broken away. v

Figure 7 is an enlarged sectional elevation view,

of a portion of Figure 4, of the device taken along the axis of the main drive shaft.

' Figure 8 is an exploded perspective view of the indicatorhand assemblies and their respective reset mechanisms.

Figure 9 is a detached front elevation view of the reset mechanism partly in section.

Referring to the drawings, in detail, in the 11- lustrated embodiment of the invention, thedevice comprises a casing I I, a frame which may be cast orotherwise formed so as to have a flat plate member l2, see Figures 3 and 5, from which e'xtends a plurality of lugs, as l3, [4,15 adapted to secure the frame to the casing, and a slotted lug it for the purpose hereinafter described. Two

flat outer frame bars l1 and l'8, shown in Figure 4 continue from each end of plate l2 substantially perpendicular with respect thereto., The generally horizontal bars I I and iii are providedwith arcuate outer surfaces to facilitate a complementary fit within a casing I l. The plate top bar H of the frame contains an elongated opening l9, see Figure 6, angularly disposed towards the rear edge of the bar for forth. v

Extendingbetween. bars l1 and i6 in spaced parallel relation to plate [2 is a fiat vertical bar 26. Plate l2 and bar 20 are provided intermediate their ends with axially aligned bearing openings adapted to receive and house bearing members 2| and 22, if desired of ball bearing type, associated with a main driven shaft 23 disposed in the frame parallel to outer frame bars l1 and I9. v

The driven shaft 29 is secured against axial thrust by mounting. bearing 2| in thebearing opening of plate l2 against annular shoulder 24 and locking the same therein by corrugated washer 25 and split ring 26 adapted to snap into an annular groove in the bore of the bearing opening. The corrugations of washer 26 permit slight axial resiliency, but prohibit any. appreciable axial movement.

The main driven shaft 23 extends-through to the outside-or front fiat face of plate I2 and bar 29. The extremity of shaft 23 outside of plate l2 carries an improved pointeror indicator mounting and operating assembly, whilethe other or rear extremity of the shaft has mounted thereon a drum pulley 21, by any suitable means such as a key 28, inFigure 7.

Specifically referring to Figure 7, the improved indicator assembly, shaft 23, as it projects from the plate l2, carries a lever 29, splined or otherwise secured, adapted to revolve in either a clockwise or counter-clockwise direction to selectively operate the maximum indicator members 36 and 3| through their associated parts. The associated parts for each maximum indicator mem- .ber co-acting with the lever 29 are substantially the same in construction and detailedreference to one set of parts therefore .will describe both.

Accordingly, leading up to such detailedreference, the shaft 23 has a reduced shaft or extremity 32 continuing from lever 29 to the exposed tip end on' which is secured an instantaneous indicator hand 33. "Freely mounted around reduced shaft 32 is a tubular shaft or elongated sleeve 34, to the exposed tip end of which is secured a maximum indicator 'hand 30. Tubular shaft 34 has an enlarged stepped annular end 'adj'acent lever .29, so as to provide annular surfaces 35, 36, and 31 The annular surface 31 is provided with an anchoring shoulder 39.

Each of the annular surfacessupports a cooperating part. Elongated annular surface 36 has freely mounted thereon an identically formed tubular shaft 39 of less length than surface 36, so as to expose the end portion of the shaft 34.

.Surface 36 is associated with a split collar 46 (see Figure 8) secured thereto, collar 46 holding the inner coiled end of winding spring 4|. Surface 31 is associated with ratchet wheel or disk 42 in mesh with a pawl 43, shown in Figures 8 and 9, and carries a pin 44 near its peripheral 'edge adapted to be acted upon by lever 29.

a purpose hereinafter setannular surfaces 36, 36 and 31, described in connection with shaft 34, and each annular surface carries a similar corresponding part, as indicated by numerals 46a, 4la, 42a, in Figure 8. L-shaped pin 44a is adapted to coact generally'similarly to pin 44 with lever 29 but for the opposite direction of movement of said lever. To permit such coaction, pin 44a is made longer than pin 44 and shaped to contact the opposite edge of lever 29.

Extending forwardly from plate I2 are spacer lugs 41 and 48, see Figure 4, to which is secured a fiat bar 50 and an indicating dial 49 traversed vertical axis of the airplane carrying the device.

The dial 49 has a centrally disposed opening in alignment with a relatively large opening in bar 59 which has a bushing 60a secured therein,

through which project the ends of the three indi-' cator hand shafts previously described. Obvi- 'ously, the indicator hands are thus in position to turn around the dial to various readings in driven shaft 23 at the inner coil end-(see Figure 7) by a sleeve 5| secured on the shaft isa coil spring 52 which is secured at the outer end of the coil by a bolt and split sleeve fastener 53 (see Figures 3 and 4), secured within the elongated slot of lug 16. Spring 62- is so set as to retain the indicator hands and a weight, hereinafter described, normally in a neutral or inoperative position. spring coils is limited by block 65, shown in Figure 6 secured to plate i2 adjacent one side of the outer coils.

Above and below drum pulley 21 and disposed from bar 26 at its point of junction with top and bottom frame bars l1 and I6 are lugs 56 and 51 respectively (see Figure 4)., in each of which are respectively secured --,pu1ley axles or shafts 58 and 59. l

Pulleys 66 and 6|, which may be ball bearing. type, are freely mounted on the shafts 58 and 69 for rotation (see Figure 2), pulley 60 being visible through angular slot l9 in top bar l1 (see Figure 6), saidslot being sufllciently large topermit'shaft 56 and pulley 66 to laterally move into alignment with the slot for adjustment of cable 62 on the pulley upon release of set screw I 63. The axes of shafts 56 and 59 are angularly disposed with respect tothe plane of .the' axis of the main shaft 23, that carries drum pulley 21 to prevent tangle or slack caused by overlapping cable and provide for a straight pull and even ceiling of cable 62 around the drum surface of pulley 21.

In the outer end of each .bar l1 and I6, secured by set screws 64 and 65 (see Figures 4-6), are the vertical parallel guide rods 66 and 61, preferably spaced farther apart than the overall .diameter of pulley 21 and the outer peripheral edges of the pulleys and 6|. The proportional spacing of guide rods 66 and 61 with respect to the foregoing elements is important for the proper installation of the mass or weight 66. v

The mass or weight 66 is designed to be a maximum for a minimum amount of cubic space. I

To provide for this, the mass is cast or cut out at the side adjacent the cable pulleys in a gen erally V-shaped well portion 69 so shaped and so proportioned, as to clear the pulleys 21, 60 and 61 during operation (see Figure 6) Centrally disposed and .projecting through the,

secured between-plate J2 and bar 20 to main Lateral displacement of the" through bezel 80 and chamber I8.

' weight 88 are stop bolts 15 and 16 adapted to limit upward thrust of the weight by contact with top bar L During operation of the present device the mstant, i. e., instantaneous valve, hand 33 moves in either direction and returns to neutral or zero position promptly in response to the tension 01 spring 52 when accelerated vertical impulses cease, but the maximum hands 38 and 3| as. they turn respectively wind springs 4| and -4la and are locked in their furthermost positions by their respective pawl and ratchet mechanisms. Hand 30 is locked by spring pressed pawl 43 engaging ratchet wheel 42 and hand 3| is locked in the same manner by the reversely rotated ratchet wheel 42a and spring pressed pawl 43a, where upon, after a specific series of indications are finished, the hands 38and 3| must be released and reset to normal position for the next dive and pull-out.

An arrangement accordingly is provided to simultaneously release both novelly mounted pawls 43 and 43a from the teeth of the ratchet wheels to reset the hands. Referring to Figures 1, 2, 3, and 9 the reset or release mechanism comprises a knob l1, a chamber 18 in an enlarged off-set portion 19 in bezel 89 and a shaft 8| projecting Bezel 80 is secured to casing It in any suitable manner, so that enlarged part '|9 lines up with an inwardly extending portion of the flange of casing through which extends shaft 8|. The shaft 8| has a lug 82 pointing towards the front of the casing secured on shaft 8| and normally held inoperative against the wall of chamber 18 by a spring 83. Shaft 8| projects inwardly through the flange of casing II at such a point that lug 82 extends into the casing between dial 49 and plate l2. Adjacent and within the radial throw of lug 82 is a bell-crank lever with arms 84 and 85 depending from a spring anchor plate 86, which plate is journalled to plate |2 by suitable means, as bolt 81, and a split'collar 88 to hold the inner coil end of spring 89 and pawl 43.

The resetting mechanism herein disclosed is claimed in my copending application bearing Serial NO. 599,001, filed on June 12,- 1945.

' Operation In reference to one feature of operation it should be noted that the maximum indicator hands in the present disclosure are directly oper- I ated by a lever 29 through a pin 44 carried by one 81, so as to normally press the pawl into engagementwith ratchet wheel 42. As the ratchet wheel 42 rotates, spring 4| winds up on shaft 34;

Arm 84 is. in the line of-travel of lug 82 and arm 85 extends across plate I 2 into contact with an arm 90 depending from the twin spring anchor plate 86a mounted on bolt 810, which is slightly longer than bolt 81. Split collar 88a, pawl 43a.

on Y and spring 89a are secured to the plate 88a in the same manner described as, in connection with plate 83. I I I In specific operation, assume the device to be properly installed in an aircraft in flight along astraig'ht path when suddenly it becomes essential to dive the craft, whereupon the plane and crew are subjected to increasing stress with the rapidity of pull-out and may be acted on by an accelerational force many times greater than that, due to gravitation, normally along the vertical axis of the craft.

Immediately that the pilot dives, weight 68 is acted upon by positive vertical accelerations, so that cable 62 is pulled about pulleys 60, 6| and 21,

whereupon main shaft 23 is rotated in a clockwise direction (Figure 5) and instantaneous indicator hand 33 carried by reduced shaft 32 is moved to give constant positive readings in units of gravity; Directly following actuation of the instant indicator hand, motion is transmitted through pin 44 to disk 42, whereupon maximum positive indicator hand 30 sweeps forward clockwise about the dial, winds spring 4| around sur- .face 36, and is held set to itsfurthermost position by pawl 43 engaging ratchet disk 42, until the pilot pulls out of thedive; whereupon the instant hand 33 returns past zero point and instantly begins to give negative indications while the maxi- 80 mum indicator'hand remains set at such maxichain of operation being identical to that just described with the exception that lever 29 moves ratchet disk 42a through vL-shaped pin 44a in a reverse direction, so as to tend to actuate maximumhand 3| in a counter-clockwise direction,

until the pilot levels off.

To reset the maximum indicator hands 30 and 3|, knob His manually rotated, shaft 8| rotates against spring 83 and lever 82 strikes arm 84 and and releases pawl 43. Simultaneously with this operation, arm 85 lifts arm 98 and similarly releases pawl43a and the maximum hands return to zero under the unwinding action of springs 4| a and 4|. I

In Figure 2, is illustrated a weight holde'r com-v prising a fiat spring 9| having one end bifurcated (not shown) 'and secured to the back of casing II by a stud 83, adapted to normally be in a retracted position against the casing wall. The spring 9| is provided at the top with an enlarged claw head 94 and a plurality of lugs 95 adapted to engage around the weightwhen the spring is forced forward by a bolt 92 passing through the casing and the stud 93 to hold the weight for shipping the device.

To illustrate an advantageof this instrument, when a dive approaches some predetermined value, the pilot knows it is time to pull out, as

during pull-out a gravitational force of from 1 to 12 times normal mustbe overcome, and it is necessary for the pilot to know whethe'r or'not his plane and crew can stand such an increase in force. The duration of the acceleration is generally so small that it would beimpossible for the pilot to read the instrument during this maneuver and therefore he must read the maximum and minimum hands after the maneuver has been completed. By associating his sensations and actions and readings of airspeed and altitude during the rotates plate 86 againstthe. action of spring 89 a dive with the accelerometer reading when the dive is completed, the pilot can predict and con- There is thus provided a novel improved and simplified accelerometer structure which may be easily and quickly calibrated, and one in which complicated damping mechanisms are eliminated and rendered unnecessary, and whereby no gears or pinions are required in the actuating mechanism between the indicating pointers and the acceleration responsive mass.

While only one embodiment of the invention has been illustrated and described, various changes and modifications, which will now appear to those skilled in the art, may be made without departing from the scope of the invention. Reference is therefore to be had to the appended claims for a definition of the limits of the invention.

What I claim is: I

1. An endless cable drive mechanism foraircraft accelerometers, including cable power transmitting means responsive to positive and negative vertical movements of an aircraft with respect to the normal flight path, cable guide pulleys disposed adjacent the limit point of movement of said transmittim, means, a cable joined together in said transmitting means, and

a relatively larger driven pulley having its axis angularly disposed in a plane between and paral lel to the axes of said guide pulleys with said cable looping and feeding around said driven pulley in coils so that the strands of the cable are in helical coil form whereby said driven pulley may be rotated in either a clockwise or counterclockwise direction.

2. An endless cable drive mechanism for aircraft accelerometers, including cable power transmitting means responsive to positive and negative movements of an aircraft with respect a dffi'en pulley disposed between said guide pulleys with said cable wrapped around said driven pulley, whereby said driven pulley may be rotated in either direction by said cable.

4. An endless cable drive mechanism for aircraft "accelerometers, including cable power transmitting means responsive to positive and negative vertical movements of an aircraft with respect to the normal flight path, said transmitting means including a weighted member, guides for said weighted member arranged to be parallel with each other, cable guide means disposed adjacent the limit points of movement of said weighted member, a cable joined together and fixed to said weighted member, and a driven pulley disposed between said guide pulleys with said cable wrapped around said driven pulley whereby said driven pulley may be rotated in either direction .by said cable, said weighted member being provided with a longitudinal recess to permit movement of said member past said driven pulley.

5. In an accelerometer, the combination comprising a cable power transmitting means responsive to positive and negative vertical movements of an aircraft with respect to the normal flight path, cable guide pulleys disposed adjacent the limit point of movement of said transmitting means, a cable joined together in said transmitting means, a relatively larger driven pulley having its axis angularly disposed in a plane between and parallel to the axes of said guide pulleys with saidcable looping and feeding around said driven pulley in coils so that the strands of the cable are in helical coil form whereby said driven pulley may be rotated in either a clockwise orcounterclockwise direction, and indicating means driven by said driven pulley to show the direction and extentof movement of said transmitting means.

6. In an accelerometer, the combination com- 40 prising, a cable power transmitting means, re-

sponsive to positive and negative vertical movements of an aircraft with respect to the normal to the normal flight path, cable guide pulleys dis- 1 posed adjacent the limit points of movement of said transmitting means, a cable joined together in said transmitting means, a relatively larger driven pulley having its axis angularly disposed -either a clockwise or counterclockwise direction,

said cable power transmitting means including a flight path, cable guide pulleys'disposed adjacent the limit points of movement of said transmitting means, a cable joined together in said transmitting means, a driven pulley disposed between said guide pulleys with said cable wrapped around said driven pulley, wherebysaid driven pulley to show the direction and extent of movement. of

said transmitting means.

weighted member to which said cable is fixed,

said member being provided with a longitudinal recess to permit movement of said member past said driven pulley, and guides for said member arranged to be parallel with each other and substantially parallel with, and in the same plane as, the path of travel of the straight portions of the cable connected to said member and between the guide pulleys.

3. An endless cable drive mechanism for aircraft accelerometers, including cable power transmitting means responsive to positive and negative vertical movements oi an aircraft with respect to the normal flight path, cable guide '7. In an accelerometer, the combination comprising a cable power transmitting means responsive to positive and negative 'vertical movements of an aircraft with respect to the normal flight path, said transmitting means including a weighted member, guides for said weighted member arranged to be parallel with each other, cable guide means disposed adjacent the limit points of movement of said weighted member,, a cable joined together and fixed to said weighted member, a driven pulley disposed between said guide pulleys with said cable wrapped around said driven pulley whereby said driven pulley may be rotated in eitherdirection by said cable, said weighted member being provided with a longitudinal recess to permit movement of said member past said driven pulley, and indicating means driven by said driven pulley to show the direction and extent of movement of said weighted mempulleys disposed adjacent the limit points of I movement of said transmitting means. a-cable joined together in said transmitting means, and

her.

JAMES E, BEVINS. 

